We introduce fracture-flip, a method to obtain high resolution views of membrane surfaces. The method, a corollary of label- fracture (Pinto da Silva & Kan, J Cell Biol. 99: 1156, 1984), is based on the stabilization of the exoplasmic halves of membranes by carbon evaporation. Inversion of these casts followed by Pt/C imaging leads to new views of the cell surface at macromolecular resolution. Because of the obvious promise of fracture-flip we redirected the activity of our section and concentrated most of our research effort in the development and application of the new method. As a result, we have now completed and sent for publication three studies that should be published before the end of 1988. The first describes Fracture-flip; the second reports the migration of surface macromolecules during the formation of coated pits in spreading macrophages; the third describes the surface of boar sperm. We have completed the experiments of other studies including: ultrastructure of the nuclear envelope; visualization of cytoplasmic surfaces of membranes comparative studies of Leishmania major from infective and non-infective phases; mast cell secretion; cell capping ultrastructure of nerve cells in culture; application of colloidal gold to fracture-flip. We are confident that fracture-flip will substitute high-resolution scanning electron microscopy and of cell surfaces will provide macromolecular resolution images of the structure and topochemistry of biological membranes.